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https://github.com/azahar-emu/dynarmic
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46eae8cf2f
Due to promotion rules (types < int, even if unsigned, get promoted to int when arithmetic is performed on them), this is a potential spot for undefined behavior.
61 lines
2.0 KiB
C++
61 lines
2.0 KiB
C++
/* This file is part of the dynarmic project.
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* Copyright (c) 2018 MerryMage
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* This software may be used and distributed according to the terms of the GNU
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* General Public License version 2 or any later version.
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*/
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#include <tuple>
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#include "common/common_types.h"
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#include "common/bit_util.h"
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#include "common/fp/fpcr.h"
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#include "common/fp/fpsr.h"
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#include "common/fp/info.h"
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#include "common/fp/op/FPRecipExponent.h"
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#include "common/fp/process_nan.h"
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#include "common/fp/unpacked.h"
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namespace Dynarmic::FP {
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namespace {
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template <typename FPT>
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FPT DetermineExponentValue(size_t value) {
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if constexpr (sizeof(FPT) == sizeof(u32)) {
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return static_cast<FPT>(Common::Bits<23, 30>(value));
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} else if constexpr (sizeof(FPT) == sizeof(u64)) {
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return static_cast<FPT>(Common::Bits<52, 62>(value));
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} else {
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return static_cast<FPT>(Common::Bits<10, 14>(value));
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}
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}
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} // Anonymous namespace
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template <typename FPT>
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FPT FPRecipExponent(FPT op, FPCR fpcr, FPSR& fpsr) {
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const auto [type, sign, value] = FPUnpack<FPT>(op, fpcr, fpsr);
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(void)value;
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if (type == FPType::SNaN || type == FPType::QNaN) {
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return FPProcessNaN(type, op, fpcr, fpsr);
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}
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const FPT sign_bits = FPT(FPInfo<FPT>::Zero(sign));
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const FPT exponent = DetermineExponentValue<FPT>(op);
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// Zero and denormals
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if (exponent == 0) {
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const FPT max_exponent = Common::Ones<FPT>(FPInfo<FPT>::exponent_width) - 1;
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return FPT(sign_bits | (max_exponent << FPInfo<FPT>::explicit_mantissa_width));
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}
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// Infinities and normals
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const FPT negated_exponent = FPT(~exponent);
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const FPT adjusted_exponent = FPT(negated_exponent << FPInfo<FPT>::explicit_mantissa_width) & FPInfo<FPT>::exponent_mask;
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return FPT(sign_bits | adjusted_exponent);
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}
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template u16 FPRecipExponent<u16>(u16 op, FPCR fpcr, FPSR& fpsr);
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template u32 FPRecipExponent<u32>(u32 op, FPCR fpcr, FPSR& fpsr);
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template u64 FPRecipExponent<u64>(u64 op, FPCR fpcr, FPSR& fpsr);
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} // namespace Dynarmic::FP
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